A stereoselective synthesis of sucrose. Part II. Theoretical and chemical considerations

Abstract

Under the agency of an iodonium ion, the tertiary anomeric hydroxyl of tetraacetyl fructofuranose adds stereoselectively in a 1,4 sense, to a pyranoid 4,6-O-benzylidenated conjugated diene receptor. The resulting disaccharide, isolated in 45% yield, is an hex-2-enopyranoside possessing an allylic primary iodide which can be oxidised to an aldehyde either directly or after hydrolysis to the allylic primary alcohol. The aldehyde is decarbonylated and the unsubstituted hex-2-enopyranoside formed undergoes hydroxylation giving exclusively the manno-diol. After protecting the equatorial hydroxyl as the benzoate ester, the axial 2-hydroxyl group is inverted via oxidation followed by borohydride reduction. Acetylation gives the known 4,6-O-benzylidene hexaacetyl derivative of sucrose, which is identified by mixture melting point.